Water-soluble corrosion inhibitors



United St 2,923,599 WATER-SOLUBLE CORROSION INHIBITORS Walter G. Toekelt, Downers Grove, Ill., ,assignor, by

mesne assignments, to. Universal Oil Products Company, Des Plaines, 111., a corporation of Delaware No Drawing. Application March 26, 1958 Serial No. 724,202

6 Claims. (Cl. 21-2-7).

This invention relates to novel. water-soluble corrosion inhibitors and to the use thereof in preventing corrosion of metallic surfaces upon. contact. withwater.

Corrosion of metallic surfaces, particularly iron and steel, in contact with fresh or salt water or various-aqueous solutions, results in a serious economical loss. There is an urgent need for, and, the present invention provides, improved water-soluble. corrosion inhibitors. which will retard and/or prevent such corrosion.

While the novel inhibitors of the present invention may be used in any system whereinwater or aqueoussolutions contact metallic surfaces, the following specificexamplesv are set for as illustrative, but not limiting, instances in which the inhibitors of the present invention are useful. Storage tanks, pipe lines and the like containing. petroleum oils or other organic compounds. generally contain. water which causes corrosion. of the metallic surfaces. ample, in storage tanks. the water settles. to the bottom and causes corrosion of the. internal surfaces of the storage tank. The water-solublecorrosion inhibitorof'the present invention will dissolve in the water phase and willserve to retard and/or prevent such corrosion. ample is in the stamping, rolling or other working of metal in which a water stream is sprayed. or otherwise. used as a coolant. Because. thesevoperations, are. -e ffected at high temperature, the cooling water often. causes extensive corrosion. Such corrosion is. avoided; bysincorporating the corrosion. inhibitor of the presentinventiom in the water spray. Still another applicationiszinthe saltice water solutions used as refrigerants, fort-example, in railroad cars, trucks, etc. whenused inarailroad.cars, the salt solution not only elfects corrosion of. the railroad cars,v but also drips onto the rails; and: causes: corrosion thereof. It is readily seen thatsuch corrosionaiszaserious economical problem because it requiresfrequent;replacement of rails, which is expensive. bothzirr manpowenand in material cost. water, acid solutions suchas pickling solutions; etc.

The novel corrosion inhibitors of the present invention are reaction products. of a tetrahydroxyalkyl. alkylenepolyamine with phytic acid. Aparticularly preferred tetra hydroxyalkyl alkylenepolyamine foruse in the present invention is N,N,N,N-tetrakis=( 2-hydroxyethyll)- ethylenediamine. -In the interestof: simplicity, thlSsGOlTlpound is referred to in the present specificatiomand-claims as tetrahydroxyethyl ethylenediamine. Other tetrahydroxyalkyl alkylenepolyamines include N,N,N',N'-tetrakis-(hydroxymethyl)-ethylenediamine, N,N,N',N-tetrakis-(Z-hydroxypropyl)-ethylenediamine, N,N,N,N-tetrakis-(3-hydroxypropyl)-ethylenediamine, N,N,N',N-tetrakis-(Z-hydroxybutyl)-ethylenediamine, N,N,N',N-tetrakis-(3-hydroxybutyl)-ethylenediamine, N,N,N',N'-tetrakis-(4-hydroxybutyl)-ethylenediamine, N,N,N,N'-tetrakis-(2-hydroxypeutyl)-ethylenediamine, N,N,N',N'-tetrakis-(3-hydroxypentyl)-ethylenediamine, N,N,N',N'-tetrakis-(4-hydroxypentyl)-ethylenediamine, N,N,N',N'-tetra leis-(S-hydroxypentyl)-ethylenediamine, etc., N,N,N,N'-

Another ex-,

Still other: applications. include boiler.

l atented Feb. 2, 1960 2, tetrakis-(hydroxymethyl)-propylenediamine, N;N-,N' ,N'- tetrakis-(Z-hydtoxyethyl)-propylei1ediamine, N,N,N ',N"- tetrakis-(2-hydroxypropyl) -propylenediarnine, N,N,N',N'- tetrakis-(3-hydroxypropyl)-propylenediarnine, N,N,N',-N"- tetral'cis-(Z-hydroxybutyl) -propylenediamine, N,N,N,N'- tetrakis-(3-hydroxybutyl)-propylenediarnine, N,- N',-Nf,N"-

'tetrakis-(4-hydroxybutyl)-propylenediamine, N,N,N-,'N-

diamine, N,N,N",N-tetrakis-(4 hydroxypentyl)-butylene= diamine, N,N,N ,N'-tetrakis-(S-hydroxypentyl)-butylenediamine, etc. Here again, in. the interest" of simplicity, these compounds'are being referred to in, the present specification and claims by the name of tetrahydroxyalkyl alkylenediamine. Y u

While the tetrahydroxyalkyl alkylenediamines;general lyare preferred; it is understood that similarly substituted dialkylenetriamines" and particularly dieth'ylenetri'amine and dipropylenetriamine, trialkylenetetraarnines and particularly triethylenetet'raamine and tripropylenetet'ra amine, tetraalkylene pentaamines and particularly tetraethylenepentaamine and tetrapropylenepentaamine, etc. may be employed for reaction with. phytic acid but not necessarily with equivalent. results. I p

The. reaction of. the tetrahydroxyalkyl alkylenepol'y amine. and phytic acid is effected using from about 0.5 to about 6 mol proportions of the tetrahydro'ityalkyl' alkylenepolyamine per 1 mol"proportion of'ph'ylt'ic acid. The reaction readily. is elfected atatmospheric' temperature although in some cases elevated temperature, which gem erally willnot exceed about 100 C, may be employed. Whenhi'ghe'r temperatures are. used, the reactionpreferablypis effected under superatmosphe'ric pressure in order tornaintain the reactants in substantially liquid phase.

While the tetrahydroxyalkyl. alkylenepolyamine and phytic acid may be reacted under anhydrous conditions, for ease ofhandlirig' andreacting, generally aqueous solutions thereof are utilized. The aqueous solution may contain from 10% to about by weight of the activecomponent. As another advantage to utilizing aqueous solutions of the reactants, the reaction product is recovered as an aqueous. solution and the aqueoussolution isuti-lized as acorrosion inhibitor, Without the' additional time and expense. otherwise. necessary to separate thereaction. prod.- uct from the aqueous solvent. When; a more dilute solution. is desired, additional water may be commingled with thereactionproduct in order to form a final solution of the desired concentrationa I s hereinbefore set forth, the reaction product is recovered and used as an aqueous solution. However, when desired, the reaction product may be separated from the aqueous solvent in any suitable manner, and the reaction product utilized as such or as a solution in other solvents as, for example, alcohols, ketoues, aldehydes, etc.

The exact composition of the reaction product has not been determined. Without any intention of being limited thereto, it is believed that the reaction product comprises a salt, although it may consist of or comprise esters, or mixtures of salts and esters. Regardless of the specific composition of the reaction product, it has been,

determined that the reaction product is an effective corrosion inhibitor, and the same is being disclosed and claimed herein for such use.

As hereinbefore set forth, the reaction product prepared in the above manner is utilized as a water soluble corrosion inhibitor. The reaction product is incorporated in water, aqueous solutions or substrates containing water in a suflicient concentration to etfectively retard corrosion of metallic surfaces. Generally, it will be utilized ina concentration of below about 1% by weight of the water, aqueous solution or substrate containing water, and more particularly in a concentration within the range of from about 0.001% to about 1% and still more particularly of from about 0.01% to about 0.5% by weight thereof, although higher concentrations may be employed when excessive corrosion is encountered. It is understood that the corrosion inhibitor may be used -in conjunction with other additives which are incorporated in the substrate for various reasons.

The following examples are introduced to illustrate further the novelty and utility of the present invention but not with the intention of unduly limiting the same.

The reaction product of the present invention was evaluated as a corrosion inhibitor by the following method. A 600 cc. beaker was used as the reaction vessel and 300 cc. of a 5% sodium chloride solution containing the inhibitor was introduced into the beaker. A 0.5" x 3" x A" mild steel strip was inserted in the beaker and held in a horizontal position with one end resting on a glass. rod. The sodium chloride solution was stirred by a single blade stirrer revolving at 250 r.p.m. Air was continuously bubbled in at the rate of 5.6 liters per hour.

When evaluated in the above manner, a steel strip, after six hours exposure in a brine not containing inhibitor, showed a weight loss of 20 mg.

Example I The reaction product of this example was prepared by reacting tetrahydroxyethyl ethylenediamine with phytic acid. To a solution of 1.4 gms. of phytic acid in gms. of water, 2 gms. of tetrahydroxyethyl ethylenediamine (N,N,N',N'-tetrakis-(2-hydroxyethyl) ethylenediamine) was added at room temperature. The reaction was slightly exothermic. The reaction product was a clear solution having a slight yellowish hue.

The reaction product, in a 50% by weight aqueous solution, was evaluated in another sample of the brine described above and in the same manner as described therein. The reaction product was used in a concentration of 0.02% by weight of active ingredient (0.04% by weight of aqueous solution). When evaluated in this manner the steel strip lost only 2.2 mg. It will be noted that the reaction product 'was very effective in retarding corrosion of the metal.

Example [I In this example the reaction product was prepared in the absence of water. Upon mixing at room temperature of the tetrahydroxyethyl ethylenediamine and phytic acid, heat is given off and a thick, gelatinous material is formed. Upon boiling, this material was converted into a tan glass. This product is soluble in water and, when prepared as an aqueous solution, is evaluated in the same manner as described in Example I for use as a corrosion inhibitor. I

Example Ill The corrosion inhibitor of this example is prepared by reacting at room temperature 1 mol proportion of N,N,N',N' tetrakis (2 hydroxyethyl) 1,3 diaminopropane with 1. mol proportion of phytic acid. The reactants are used as aqueous solutions of 50% concentration, and the reaction product is recovered as an aqueous solution. The, reaction product is evaluated as a corrosion' inhibitor in the same manner as described in Example I. -.'1 'he loss'in weight of the steel strip is reduced considerably:belowwthe 20 mg. loss obtained in the absence of the inhibitor,

I claim as my'invention.

l. The method of retarding corrosion of a ferrous metal upon contact with water which comprises effectingsaid contact in the presence of a water-soluble corrosion inhibitor comprising the product formed by the reaction of from about 0.5 to about 6 mol proportions of a tetrahydroxyalkyl alkylenepolyamine with 1 mol proportion of phytic acid, the first-mentioned compound containing from 2 to 5 amine groups per molecule and having from 1 to 5 carbon atoms in each of the alkyl groups and from 2 to 4 carbon atoms in the alkylene group.

2. The method of retarding corrosion of a ferrous metal upon contact with water which comprises effecting said contact in the presence of a water-soluble corrosion inhibitor comprising the product formed by the reaction of from about 0.5 to about 6 mol proportions of tetrahydroxyethyl ethylenediamine with 1 mol proportion of .phytic acid.

3. The method of retarding corrosion of a ferrous metal upon contact with water which comprises effecting said contact in the presence of water-soluble corrosion inhibitor comprising the product formed by the reaction of from about 0.5 to about 6 mol proportions of tetrahydroxyethyl propylene diamine with 1 mol proportion of phytic acid.

4. Water containing as a corrosion inhibitor the product formed by the reaction of from about 0.5 to about 6 mol proportions of a tetrahydroxyalkyl alkylenepolyamine with 1 mol proportion of phytic acid, the firstmentioned' compound containing from 2 to 5 amine groups per molecule and having from 1 to 5 carbon atoms in each of the alkyl groups and from 2 to 4 carbon atoms in the alkylene group.

5. Water containing as a corrosion inhibitor the product formed by the reaction of from about 0.5 to about 6 mol proportions of tetrahydroxyethyl ethylenediamine with 1 mol proportion of phytic acid.

6. Water containing as a corrosion inhibitor the product formed by the reaction of from about 0.5 to about 6.mol proportions of tetrahydroxyethyl propylenediamine with 1 mol proportions of phytic acid.

References Cited in the file of this patent UNITED STATES PATENTS 2,626,238 Artz c June 20, 1953 2,697,118 Lundsted et al Dec: 14, 1954 2,755,304 Bersworth et al. July 17, 1956 

1. THE METHOD OF RETARDING CORROSION OF A FERROUS METAL UPON CONTACT WITH WATER WHICH COMPRISES EFFECTING SAID CONTACT IN THE PRESENCE OF A WATER-SOLUBLE CORROSION INHIBITOR COMPRISING THE PRODUCT FORMED BY THE REACTION OF FROM ABOUT 0.5 TO ABOUT 6 MOL PROPORTIONS OF A TETRAHYDROXYALKYL ALKYLENEPOLYAMINE WITH 1 MOL PROPORTION OF PHYTIC ACID, THE FIRST-MENTIONED COMPOUND CONTAINING FROM 2 TO 5 AMINE GROUPS PER MOLECULE AND HAVING FROM 1 TO 5 CARBON ATOMS IN EACH OF THE ALKYL GROUPS AND FROM 2 TO 4 CARBON ATOMS IN THE ALKYLENE GROUP. 